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Determination of the Optimum Base Characteristics for Pavements (TR-482)

Two buckets of aggregate, one with fewer fines

Quarry aggregate sample on left side and aggregate from trimmer on right side



Aggregate placed on the base layer from trimmer (left) and from quarry (right)



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Student researcher:

Project status


Start date: 08/15/02
End date: 02/14/04


Report: Final Report: Determination of the Optimum Base Characteristics for Pavements (TR-482) (11.9 mb pdf) May 2004

Related publications:


Sponsor(s): Iowa Highway Research Board

About the research


In recent years, it has become apparent that the design and maintenance of pavement drainage extends the service life of pavements. Most pavement structures now incorporate subsurface layers. Part of the function of these subsurface layers is to drain away excess water, which can be extremely deleterious to the life of the pavement. To assure the effectiveness of such drainage layers after they have been spread and compacted, simple, rapid, in-situ permeability and stability testing and end-result specification are needed. This report includes conclusions and recommendations related to four main study objectives:

  1. Determine the optimal range for inplace stability and in-place permeability based on Iowa aggregate sources;
  2. Evaluate the feasibility of an air permeameter for determining the permeability of open and well-graded drainage layers in situ;
  3. Develop reliable end-result quality control/quality assurance specifications for stability and permeability;
  4. Refine aggregate placement and construction methods to optimize uniformity.